Generalization of shadow filters in fractional domain
Garima Varshney, Neeta Pandey, Rajeshwari Pandey
Abstract
Abstract This work is intended to generalize the design of shadow filters to the fractional‐order domain. Shadow filters, in integer‐order domain, introduced by Lakys and Fabre, consist of an external amplifier in the feedback loop of the basic filter cell and by varying the gain of this amplifier the parameters of the resulting filter are modified without disturbing the active and passive components of the filter itself. In particular, we consider here the case where a basic 2 α order filter is constructed using two fractional‐order capacitors both of the same order α . Mathematical formulations are drafted for pole frequency and pole quality factor for different feedback signals with various cases of stability and demonstrated using MATLAB simulations. Functional verification of the proposed theory is verified using an active filter example, designed around operational transconductance amplifier (OTA), through SPICE using 180 nm CMOS technology model parameters.